AP2 Ch28 Reproductive System (Male)

sperm (spermatozoa)

male gamete

• no ER or Golgi apparatus = slimmer for speed, short lifespan

oocyte

immature form of female gamete

ovum

mature form of female gamete

zygote

formed when sperm unites with ovum

embryo

formed when zygote attaches to uterus wall

fetus

8+ week old embryo

testes

2 flattened egg-shaped tissues located inside scrotum but hangs outside body; form inside the body and moves inferiorly out of body until birth

spermatic cords

provide blood vessels, nerves, and lymphatic vessels that supply the testes, which is wrapped in muscle and connective tissue

raphe

thickening of skin that divides 2 testes

cremaster muscle

located deep in dermis and contracts during sexual arousal or in response to temp; moves testes closer to / further from the body

dartos muscle

smooth muscles covering testes that produces wrinkled skin of scrotum when relaxed

tunica albuginea

dense layer of connective tissue with collagen fibers that covers the testes; extend into the center of testes and forms partitions called septa

septa

divides the testes into a series of lobules that contain seminiferous tubules

seminiferous tubules

site of sperm production; connect to rete testis; contain cells of leydig, which produce androgens

efferent ductiles

connect the rete testis to the epididymis

spermatogenesis

process in seminiferous tubules that produces spermatozoa; begins in outermost layer of cells in seminiferous tubules and proceeds toward lumen

1. spermatogonia (stem cells) divide by mitosis to produce daughter cells, some of which differentiate into primary spermatocytes

2. primary spermatocytes begin meiosis I and divide into secondary spermatocytes, which undergo meiosis II to become spermatids

3. spermatids undergo spermiogenesis to become spermatozoa

mitosis (spermatogonial phase)

spermatogonia undergo cell division through lifetime of male; a daughter cell is pushed towards the lumen (opening) of seminiferous tubule and differentiates into primary spermatocyte

meiosis (spermatocyte phase)

2-stage cell division of gametes, which only contain half the number of chromosomes (23) that normal cells (46) possesses; begins with primary spermatocytes that produce spermatids

meiosis I

meiosis stage: reduces the number of chromosomes in a cell from 46 to 23 by separating homologous chromosomes into different cells

meiosis II

resembles mitosis in every way, except the chromatids are separated into 4 cells

spermiogenesis (spermatid phase)

spermatids are small unspecialized cells, which now undergo this process to differentiate into physically mature spermatozoa (specialized cells)

head

sperm region: contains the nucleus and the chromosomes; the acrosomal cap located at tip of head contains enzymes important in fertilization

midpiece

sperm region: contains numerous mitochondria to provide ATP for movement of tail

tail

sperm region: the only flagellum in human body; lets sperm move

seminal vesicles

gland: 60% of volume; fructose, prostaglandins, fibrinogen

prostate gland

gland: 25% of volume, seminalplasmin (antibiotic)

bulbourethral gland

gland: 10% of volume, neutralizes urinary acids, lubricates the tip of the penis

epididymis

3 functions:

• monitors and adjusts the composition of seminal fluid

• recycles damaged spermatozoa

• stores and protects spermatozoa

ductus deferens

16-18”; extends from epididymis into pelvic cavity; stores sperm and conveys sperm from the epididymis toward the urethra

urethra

8-10”; conveys both urine and semen (at different times) outside of the body; has three sections: prostatic, membranous, penile

epididymis

4 cm long on posterior side of each testis; stores immature sperm after production, allowing them to become motile and fertile

1 month

How long can spermatozoa be stored in the epididymis before the body breaks it down and reabsorbs it?

ductus deferens; seminal vesicle; ejaculatory duct; prostate gland; urethra

Upon ejaculation, the smooth muscle of the epididymis walls contract and expels sperm to the _____ _____, whose smooth muscle walls create peristaltic waves to squeeze the sperm toward where it joins with the _____ _____ (together called the _____ _____), which then passes through the _____ _____ and merges with the _____.

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prostate gland; penis; external urethral orifice

The urethra passes down through the _____ _____ (gland) and then through the _____ to the _____ _____ _____.

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internal urethral spincter

smooth muscle sphincter that prevents urine expulsion during ejaculation

semen

mix of seminal fluid, sperm, and enzymes; 2-5 mL released upon ejaculation

20-100 million

How much spermatozoa is in each mL of semen?

seminal fluid

fluid component of semen that contains nutrients (carbs), ions, and enzymes; pH 7.2-7.7

• provides a transportation medium for sperm

• carbs provide for sperm’s ATP production

• enzymes activate sperm to make them motile and fertile

seminal enzymes

includes:

• proteases, which dissolves mucus in the vagina

• seminalplasmin, which kills microbes

• enzyme that converts fibrinogen to fibrin

• fibrinolysin, which liquifies clotted semen

penis

external genitalia: delivers sperm into female reproductive tract; prepuce covers glans penis and can be removed shortly after birth; internally, it contains the urethra and 3 columns of erectile tissue: corpus spongiosum, 2x corpora cavernosa

erectile tissue

spongy tissue consisting of connective tissue and smooth muscle permeated with vascular sinuses

vascular sinuses

fill with blood during sexual arousal; expansion compresses veins to keep blood in penis, causing erection

sympathetic

Which nervous system causes ejaculation?

GnRH

hormone: stimulates the production of FSH and LH

FSH

hormone: targets sustentacular cells, which cause synthesis of ABP, spermatogenesis and spermiogenesis, and secretion of inhibin

• release is stopped by testosterone and inhibin (negative feedback system)

LH

hormone: targets interstitial cells, which causes testosterone production; negative feedback system with inhibin:

• if it increases above normal, then inhibin increases to lower it

• if it decreases below normal, then inhibin decreases to raise it